When transmitting a video stream in a network, several technical solutions are known to ensure a level of quality or react when the expected level is no longer guaranteed. For example, in an IP Multimedia Subsystem (IMS) or LTE network, during call setup, codecs are negotiated (SDP negotiation) to obtain an agreement between end users and the network. Within Media Server (MRF Network Element, Media Resource Function of IMS) or in end user terminal themselves, some synchronization mechanisms, predictive or corrective algorithms are known that can be used for maintaining a desired level of quality. Examples are audio and video synchronisation using real time control protocol (RTCP) and packet loss concealment (PLC). However, these various technical solutions are limited by the physical capacity of the network.
In case the quality of a video stream is insufficient, a possible reaction is to cancel transmission of the video stream (and transmitting only audio) or replacing the video stream with a predetermined video stream, for example an avatar. However, in that case, the user has no information about the video stream.